While not a part that typically shows signs of wear, we have found that the O-rings can become degraded though the use of some solvents or Super Lube (the blue stuff, in a tube, that sometimes comes with new airbrushes). Super Lube will leave a gummy residue that is not removable.

This is seldom a problem until you wish to upgrade to a Blair SoftSpring. The reduced tension of the SoftSprings are not designed to compensate for the gumminess left behind by the introduction of Super Lube.